Attention: TDR Forum Junkies 
Originally posted by Gary - KJ6Q:
"Your absolutely right about the extended intervals with petroleum oils. . Most times it just isn't cost effective to do so. "
YEAH, that's the way I see it too, so far. After all, why absorb the added expense of regular oil analysis in order to be assured you're not exceeding your oil's capability, when with conventional oils, it pretty cheap to merely CHANGE the oil - and not MUCH more expensive than the cost of analysis!#ad
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Another reason that extended drain intervals using dino oil likely don't work is because dino oils are 'fractionally distilled', meaning that the 40-weight oil that is produced actually has lighter componenets that boil off - the consistency changes. A 10W40 dino oil could end up being closer to 20W50 (or thicker) once the lighter stuff has evaporated. The measured thickness of the oil is the average of all its components.
Synthetic oil molecules are manufactured to a specific length/size; the processes, while inherently imperfect physical operations, are fairly accurate. The consistency of the oil is much better than distilled oil.
Better filtering certainly will help any lubricating fluid. But it still remains that dino oil is not as good as synthetic.
There are other reasons for using extended drain intervals. Reduced waste oil is one.
Reduced maintenance time is another; some of us are too busy or too forgetful to remember to change the oil every 6K miles. Reduced air pollution is another reason; synthetic oils usually have around 6% points less evaporation over time - in our trucks, that's about 2/3 quart less oil evaporating into the air when using synthetics. A final reason is that, with slightly extended drain intervals, synthetic can be more cost-effective than dino oil.
Those are the main reasons *I* use Amsoil with bypass filtration in my truck. I've got 26K miles on the oil now. And I'm not planning on changing it until the analysis tells me to. I've got 90K miles on the truck now, in 3. 5 years; the Mexican-assembled truck is holding up *very* nicely - I'll be keeping it for a number of years yet.
Dino v. Synth is very nearly a religious issue. So I shall only proffer my thoughts on the topic; I'll not attempt to convert you. Besides, there are at least a million people out there who would gladly switch; a good marketer would go after them first. Besides, I'm an engineer; we-types are notoriously poor at convincing Doubting Thomases of anything!
Fest3er
